Extracorporeal circulation is and has been a routine procedure in the operating room for several years. An important component in providing extracorporeal circulation is the blood oxygenator. The function of the oxygenator is to place oxygen in close relationship to the venous blood such that the oxygen reacts with the hemoglobin with resultant absorption of the oxygen and release of carbon dioxide. For an interesting historical survey of blood oxygenators see the article published in the December, 1961 issue of Surgery entitled "Theme and Variations of Blood Oxygenators" by Richard A. DeWall, M.D., et al.
Three principal types of blood oxygenators are known in the art:
1. In the membrane oxygenator, a membrane separates the blood from the oxygen and gas exchange takes place by diffusion through the membrane. One type of membrane oxygenator is described in U.S. Pat. No. 3,413,095--Branson.
2. A film oxygenator exposes a thin film of blood to an oxygen atmosphere. One type of film oxygenator is described in the Dec. 15, 1956 issue of The Lancet, page 1246 in the article entitled "Design of an Artificial Lung Using Polyvinyl Formal Sponge".
3. The bubble oxygenator introduces bubbles of oxygen directly into the blood. In the bubble oxygenator described in U.S. Pat. No. 3,578,411, the bubble chamber has a continuous convoluted path to promote the intermixing of the blood and oxygen. U.S. Pat. No. 3,807,958 describes a bubble oxygenator which employs a plurality of vertical tubes through which the blood and oxygen mixture rises in a slug flow. U.S. Pat. No. 3,898,045 describes a bubble oxygenator having a lattice chamber tightly packed with spherical beads to provide what the patentee describes as a "wiped film bubble oxygenation process". In still another type of bubble oxygenator described in an article published in Surgery, August, 1957 entitled "Preliminary Studies On the Sponge-Oxygenator" by Adriano Bencini, M.D., et al, a long multi-perforated needle is inserted into a cylindrical piece of polyurethane sponge.
The oxygen used in blood oxygenators is quite often mixed with an anesthesia gas. In those states and foreign countries which have laws prohibiting the open venting of anesthesia gas, it is necessary to remove this gas mixture from the oxygenator by means of a vacuum source. To this end, various types of gas venting configurations have been developed to allow a vacuum exhaust without imparting a negative pressure to the interior of the oxygenator. To date, such gas vents have been in the form of separate components which are attached to the oxygenator when needed.